And over this band [of martyrs], dearly-beloved, whom God has set forth for our example in patience and for our confirmation in the Faith, there must be rejoicing everywhere in the commemoration of all the saints, but of these two Fathers' excellence we must rightly make our boast in louder joy, for God's Grace has raised them to so high a place among the members of the Church, that He has set them like the twin light of the eyes in the body, whose Head is Christ. About their merits and virtues, which pass all power of speech, we must not make distinctions, because they were equal in their election, alike in their toils, undivided in their death. But as we have proved for ourselves, and our forefathers maintained, we believe, and are sure that, amid all the toils of this life, we must always be assisted in obtaining God's Mercy by the prayers of special interceders, that we may be raised by the Apostles' merits in proportion as we are weighed down by our own sins.
St. Leo the Great, Sermon 82 (On the Feast of Ss. Peter and Paul).